Plate Tectonics

New Zealand is located on the boundary between two of the Earth's great tectonic plates - the Australian and the Pacific. Tectonic plates behave like rigid shells that slide over the surface of a sphere.

Broadly speaking, the Australian plate is heading north while the Pacific plate is heading west. The combination of these motions means that the Pacific plate, which includes much of the South Island, is moving relative to the Australian plate at a rate of about 40 millimetres each year in a southwesterly direction. So Christchurch is moving away from Auckland about 4 metres every century.